06-4 Talking COSEM over power line carrier
With the growing use of DLMS/COSEM (IEC 62056), we have received several questions concerning the possibility of reading meters over power lines.
One of the strengths of DLMS/COSEM is that application modelling is well separated from the communication profiles. Therefore, application data can be easily transported over various media.
The application is modelled by mapping application-relevant information to attributes and methods of appropriate COSEM objects like Registers, Clocks, Scripts, Profiles etc.
Data exchange takes place then by reading or writing the attributes and activating the methods necessary, using xDLMS services provided by the COSEM Application layer. For any communication profile, the connection and data-transfer services of the application layer are mapped to the services of supporting lower layers. Currently, this mapping is defined for two communication profiles: the 3-layer, connection-oriented HDLC based profile and the TCP-UDP/IP based profile and new profiles can be added when needed.
The same COSEM object model can also be used with the communication profiles specified in the Distribution Line Message Specification standard, the IEC 61334 series. This is possible because COSEM specifies how the attributes and methods of COSEM objects can be mapped to DLMS Named Variables, and the COSEM Application layer uses the same Read, Write, UnconfirmedWrite and InformationReport data communication services as IEC 61334-4-41.
The IEC 61334 series specifies various communication profiles for power line carrier, - including the S-FSK, FSK, SS-AW, SS-FFH and MCM profiles.
Thus, it is possible to exchange data with meters using the COSEM object model either using the communication profiles specified in the IEC 62056 series or the ones specified in the IEC 61334 series, although some of the more advanced features are available only in IEC 62056.